JP3192274B2 - Method for producing glass material for molding optical elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass material for molding an optical element such as a reheat press for a highly accurate optical glass element such as a lens or a prism.

[0002]

2. Description of the Related Art In recent years, optical glass lenses have become more aspherical so that both the simplification of the lens structure of optical devices and the reduction of the weight of lens members can be achieved at the same time. As a method of manufacturing this aspheric lens, after cutting a material from a glass block, rod, plate, or the like, grinding and polishing, or pressing molten glass in advance with a mold having a shape close to the lens to be manufactured, Conventional methods of manufacturing an optical lens such as grinding and polishing a glass molded body are conceivable, but since processing and mass production are difficult, a molding method for directly obtaining a lens shape using a mold is promising in recent years. Have been.

[0003] A molding method using a mold includes a direct pressing method in which a molten glass is directly pressed to obtain a high-precision optical glass element, and a high-precision optical method in which a glass material of a preform used for molding is heated and then pressed. There is a reheat press method for obtaining a glass element.

According to the former method, it is possible to manufacture a very inexpensive optical glass element. However, since high-temperature molten glass is used, it is difficult to improve the precision of the formed glass, There are also many technical problems such as a shortened life and it is difficult to put it to practical use.

According to the latter method, the problem of the direct press method is improved, but the process for manufacturing the glass material is almost the same as the process for manufacturing the polished lens, so that a relatively high cost is required. Was. The simplification of the process of manufacturing a glass material for reheat pressing is an important issue in manufacturing an optical glass element.

As an effective method for easily forming a glass material, there has been proposed a method in which a molten glass lump is dropped on a receiving mold and left as it is to form a shape, and this method is very inexpensive. A glass material for a reheat press can be manufactured (for example, JP-A-61-146721,
JP-A-2-34525 and the like).

[0007]

The molten glass can be dropped onto the receiving mold by cutting the molten glass flowing down from the glass outlet of the glass melting furnace with a cutting blade, or by melting the molten glass accumulated in the glass outlet. There is a method in which the glass is naturally dropped as molten glass by its own weight and dropped.

FIG. 5 shows a conventional method for producing a glass material by cutting a molten glass flow with a cutting blade. FIG.
(A) shows the installation state of the molten glass 1 flowing down from the glass outlet 10 of the glass melting furnace and the cutting blade 13. FIG.
(B) shows a state where the molten glass 1 is cut by the cutting blade 13 and dropped on the receiving mold 11. FIG. 5C shows a portion of a defect 5 generated in the glass material 1. When the molten glass stream is cut by a cutting blade to drop a predetermined weight of molten glass lump, a defect 5 called a so-called shear mark such as a contraction mark due to rapid cooling, a scratch, a bubble, etc., is always present on the glass surface or inside the glass contacted by the cutting blade. Had occurred.

FIG. 6 shows a conventional method of producing a glass material by cutting a molten glass flow by natural dropping of molten glass by its own weight. FIG. 6A shows a state of the molten glass 1 flowing down from the glass outlet 10 of the glass melting furnace.
FIG. 6B shows a state in which the molten glass 1 is cut by its own weight, and the molten glass lump 1 falls on the receiving mold. FIG.
(C) shows a portion of the defect 5 generated in the glass material 1.

When the molten glass flow is cut by its own weight and the molten glass is dropped, the force of pulling by the own weight of the glass that is about to drop and the surface tension of the glass that is going to return to the glass outlet at the vicinity of the cut portion is inevitable. work. Then, the diameter of the glass flow near the cutting portion becomes narrower, leading to cutting. The glass surface in the vicinity of the cut portion 3 is deformed into a thin linear shape or a minute projection, so that it is very easy to cool, and a temperature difference occurs on the surface of the falling glass.

When the glass falls into the receiving mold in such a state, the vicinity of the low temperature cut portion 3 is caught in the high temperature glass by the impact of the drop. Fatal defects as optical glass materials such as bubbles and bubbles were generated inside the glass.

When the entire surface temperature of the glass is dropped below the softening temperature, not just in the vicinity of the cut portion, the shape of the glass that drops in a drop shape is the surface tension of the glass even when the glass falls into the receiving mold. As a result, it is not possible to restore to the desired shape, and as shown in FIG.
There were problems such as remaining.

[0013] Defects formed on the surface and inside of the glass could not be removed even when the glass material produced by the above method was molded with a lens mold.

An object of the present invention is to solve the above-mentioned problems and to provide a low-cost and defect-free method for producing a glass material for molding an optical element.

[0015]

According to the present invention, there is provided a method of manufacturing a glass material for molding an optical element, wherein the molten glass flowing down from a glass outlet of a glass melting furnace is cooled by receiving a mold. In the method of manufacturing a glass material for molding an optical element, the distance between the receiving die and the glass outlet is such that the molten glass that has flowed into the receiving die is naturally cut by its own weight and surface tension, and the temperature of the flowing molten glass near the cut portion is low. Is within a region not lower than the softening temperature.

In the above configuration, it is preferable to heat the vicinity of the cut portion of the molten glass flowing down from the glass outlet to a temperature higher than the softening temperature of the glass. More specifically, the temperature near the cut portion of the molten glass is preferably in the range of 700 to 1000C.

In the above structure, it is preferable that the temperature of the receiving mold is controlled to receive the molten glass.

In the above-mentioned structure, it is preferable that the region of the glass temperature equal to or higher than the softening temperature is equal to or lower than 4.5 × 10 ⁷ poise in terms of the viscosity of the glass.

In the above structure, the temperature of the molten glass in the glass melting furnace is preferably 500 to 1300 ° C.

In the above structure, the crucible of the glass melting furnace and the outlet of the glass are preferably made of platinum.

In the above structure, the receiving mold is preferably present in a non-oxidizing atmosphere. Here, the non-oxidizing atmosphere is, for example, an inert gas such as nitrogen, argon, or helium, or a mixture of these inert gases with hydrogen as appropriate, and can prevent deterioration of the receiving mold.

In the above construction, the distance between the glass outlet and the receiving die is kept constant, and the position of the receiving die is adjusted so that the weight accuracy of the glass material for molding an optical element is within 1% by weight of the predetermined glass weight. Preferably, control is performed. When precision glass molding is performed, the performance varies depending on the glass weight system. Therefore, the distance between the glass outlet and the receiving mold is set to a predetermined height so as to fall within a range of 1% by weight of the predetermined glass weight. It is held and height variations due to the influence of heat are sequentially measured and adjusted. The distance between the glass outlet and the receiving mold is preferably selected from the range of 10 to 100 mm.

In the above structure, it is preferable to control the thickness of the optical element molding glass material by the wettability with the molten glass of the receiving mold. For example, the receiving mold is carbon with poor wettability with molten glass, boron nitride,
If at least one selected from aluminum nitride, chromium nitride, stainless steel, nichrome, glassy carbon, and silicon carbide is used, a relatively thick lens can be formed.
Conversely, if the receiving mold is coated with a chemically stable thin film having good wettability with the molten glass, a relatively thin lens can be formed. In the above, the thin film covering the surface of the receiving mold is a noble metal-based alloy thin film containing at least one or more metals among tungsten, tantalum, rhenium, hafnium, platinum, palladium, iridium, rhodium, osmium, and ruthenium. It is preferable because it is chemically stable and hardly causes corrosion.

Further, in the above structure, the temperature of the receiving mold is a temperature at which the molten glass and the receiving mold can be released after cooling of the molten glass without fusing, so that the molding cycle can be improved and efficient production can be achieved. Preferred for. Specifically, the temperature of the receiving mold is preferably 700 ° C. or lower, and may be about room temperature (room temperature).

In the above-mentioned configuration, it is also preferable that the receiving mold receives the molten glass with a heat distribution. Specifically, it is preferable to embed separate heaters in the central portion and the peripheral portion of the receiving mold, and maintain the central portion at a relatively low temperature and the peripheral portion at a relatively high temperature. This prevents the temperature of the drop center from rising at the moment when the molten glass falls into the receiving mold, and eliminates the distribution of heat in the receiving mold and reduces the variation, so that the cooling rate of the glass surface is uniform. Can be As a result, the internal distortion of the glass molded body can be reduced.

In the above structure, the surface roughness of the receiving mold is preferably a mirror surface having a center line average roughness (Ra) of 2 μm or less, because the surface of the formed glass becomes smooth.

In the above structure, after receiving the molten glass, the cooling rate of the surface in contact with the receiving mold is adjusted so as to match the cooling rate.
It is preferable to control the ambient temperature of the surface not in contact with the receiving mold. In this way, the variation in the cooling rate of the glass surface can be suppressed, and the internal distortion of the glass molded body can be reduced.

[0028]

According to the above construction, when the falling molten glass is received on the receiving mold, the state where the molten glass is dropped on the receiving mold is continuously connected to the glass accumulated at the glass outlet in a linear manner. Since it is in the state, the temperature difference near the cut portion is unlikely to occur with the glass dropped on the receiving mold. At this time, the glass temperature near the cut portion of the glass flow is the softening temperature (the viscosity of the glass is 4.5 ×
The falling temperature and the falling distance of the glass are set so as to be 10 ⁷ poise or more, so that the glass is easily cut by its own weight and surface tension.

The glass flow naturally cut by the surface tension of the glass dropped on the receiving die and the surface tension of the glass remaining at the glass outlet is instantaneously taken into the glass on the receiving die, so that no temperature difference occurs. No defects occur inside the glass. Even if the temperature in the vicinity of the cutting part becomes lower than the falling temperature of the glass, if the temperature of the receiving mold is cooled by setting the receiving mold to an appropriate temperature, the temperature difference disappears and the glass material is defective. Nothing.

Alternatively, the molten glass that has flowed down to the receiving mold is naturally cut by its own weight and surface tension, and the temperature of the flowing glass near the cut portion is determined by the ambient temperature, the flowing temperature of the glass, the weight of the glass, and the falling distance. In order to ensure that the temperature is equal to or higher than the softening temperature without being affected by such conditions, if the vicinity of the cut portion is forcibly heated to a temperature equal to or higher than the softening temperature of the glass, a glass material having no defect inside the glass can be obtained. Can be manufactured stably.

When the glass material thus obtained is used for forming an optical glass element, an extremely high-precision optical glass element can be obtained only by pressing.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for producing a glass material according to the present invention will be specifically described below with reference to the drawings.

Example 1 FIG. 1 is a process chart of a method for manufacturing a glass material according to an example of the present invention. 1 is glass (molten glass, glass material), 2 is a cut portion, 3 is near a cut portion, 4 is the surface tension of glass, 10 is a glass outlet, 11
Indicates a receiving mold. The symbol h in FIG. 1 indicates the falling distance of the glass from the tip of the glass outlet to the upper surface of the receiving mold.

FIG. 1A shows a glass melting furnace (not shown).
The state of the molten glass 1 flowing down from the glass outlet 10 of FIG. Usually, after melting and melting a glass in a melting temperature range (500 to 1300 ° C.) of various optical glasses by a glass melting furnace, the temperature of the glass outlet is set according to the properties and outflow amount of the glass. The glass flows down from the glass outlet. It is preferable that the crucible and the glass outlet of the glass melting furnace be made of platinum which is less corroded by glass. If the tip inside diameter of the glass outlet is too large, the flow output of the glass will be larger than the surface tension of the glass,
Since the glass becomes laminar and cannot flow down in the form of drops, the inside diameter of the tip of the glass outlet is reduced according to the surface tension and weight of the glass.

FIG. 1B shows a state in which the molten glass 1 has dropped onto the receiving mold 11 by its own weight. As shown in FIG. 1 (b), even if the glass 1 falls into the receiving mold, the falling distance h is such that the glass 1 can be linearly connected to the glass accumulated at the glass outlet.
Depends on the weight and temperature of the glass to be dropped or the properties of the glass. Usually, the longer the amount of glass to be dropped, the lower the glass temperature and the higher the viscosity, the longer the drop distance h. Further, in the properties of the glass, for example, the drop distance h is longer in a lanthanum-based glass having a large surface tension, and the drop distance h is short in a heavy flint glass having a small surface tension. In order to make the temperature near the cut portion 3 of the glass almost equal to the temperature difference between the glass dropped on the receiving mold and the softening temperature or higher, the flowing temperature of the glass is increased,
It is better to shorten the falling distance h. It is desirable to appropriately select the above conditions depending on the type and weight of the optical glass.
If the appropriate drop distance is determined by the type and weight of the optical glass, the height of the receiving mold 11 is kept constant without changing the height. This is because the weight of the glass may fluctuate due to the fluctuation of the height of the receiving mold, and the weight accuracy may deteriorate.

FIG. 1C shows the state of the glass 1 naturally cut from the cutting section 2 by the surface tension 4 of the glass 1 dropped on the receiving mold 11 and the surface tension 4 of the glass accumulated in the glass outlet 10. Show. The condition under which the glass is easily cut naturally when the glass is dropped on the receiving mold is preferably that the surface tension of the glass is large and the viscosity of the glass is low. The receiving die is processed in accordance with the desired shape of the glass material, and is heated in advance to prevent cracking of the glass dropped on the receiving die due to rapid cooling. In addition, when the temperature near the cutting portion becomes lower than the dropping temperature of the glass, if the temperature of the receiving mold is appropriately controlled and the glass dropped on the receiving mold is cooled, the cutting portion that flows down with a delay. There is no difference in temperature with the glass nearby, and no defects occur in the glass material.

FIG. 1D shows the shape of the glass material 1 after the vicinity 3 of the naturally cut glass has been instantaneously taken into the glass 1 on the receiving mold.

Hereinafter, the manufacturing method shown in FIG. 1 will be described in more detail. The receiving die 11 is made of austenitic stainless steel (SUS31) having a transfer surface having a size of φ10 mm at the center.
6) is selected, and the molten glass is silicon oxide (SiO ₂ ) 3
A barium borosilicate glass containing 0% by weight, 50% by weight of barium oxide (BaO), 15% by weight of boron oxide (B ₂ O ₃ ), and the balance consisting of trace components was used. 12 this glass
Outlet 1 maintained at 1000 ° C after melting at 50 ° C
From 0 to about 1 gram of the molten glass 1 flows out in the form of a drop, and is supplied to the receiving mold 11 heated to 350 ° C. in advance with a falling distance h of 50 mm. The glass was cooled on a receiving mold to produce a glass material 1.

The glass material 1 obtained according to the present example was observed with an optical microscope and found that the glass material 1 had scratches on its surface and inside.
No defects such as striae and bubbles were found. By molding this glass material, an excellent optical glass element could be obtained.

Example 2 Glass materials having different glass compositions were produced by using the manufacturing method shown in FIG. Receiving mold 11
Is a silicon carbide (Si) having the size of the central portion φ10 as a transfer surface.
C) is selected and the molten glass is silicon oxide (SiO ₂ ) 5
2% by weight, 6% by weight of potassium oxide (K ² O)
A heavy flint glass consisting of 35% by weight of lead, lead oxide (PbO) and the balance of trace components was used. After melting this glass at 1250 ° C., about 1 gram of molten glass 1 flows out in a drop form from an outlet 10 maintained at 900 ° C. The dropping distance h is set to 30 mm and supplied to the receiving mold 11 preheated to 350 ° C. The glass was cooled on a receiving mold to produce a glass material 1.

As a result of observing the glass material 1 obtained in this example with an optical microscope, it was found that
No defects such as striae and bubbles were found. By molding this glass material, an excellent optical glass element could be obtained.

(Embodiment 3) FIG. 2 is a process chart showing a method of manufacturing a glass material according to another embodiment of the present invention.

1 is glass (molten glass, glass material),
Reference numeral 2 denotes a cut portion, 3 denotes a vicinity of the cut portion, 4 denotes a surface tension of glass, 10 denotes a glass outlet, 11 denotes a receiving mold, and 12 denotes a heating means.

The symbol h in FIG. 2 indicates the falling distance of the glass.

FIG. 2 (a) shows a state where the molten glass 1 flowing down from the glass outlet 10 of the glass melting furnace and the heating means 12 are installed. The heating means 12 is used to cut the falling glass 2
Is disposed at a position where the vicinity 3 of the cut portion (the portion where the glass flow becomes thin) including the above can be heated.

FIG. 2B shows a state in which the molten glass 1 has dropped onto the receiving mold 11 by its own weight and a heating section of the glass by the heating means 12. It is desirable to surround the vicinity 3 of the cut portion of the falling glass with a heat insulating wall having a heating means in order to reduce the influence of the ambient temperature. Further, the size of the heating means is changed according to the falling distance h.

FIG. 2C shows the state of the glass 1 naturally cut from the cutting section 2 by the surface tension 4 of the glass 1 dropped on the receiving mold 11 and the surface tension 4 of the glass accumulated in the glass outlet 10. Show.

FIG. 2D shows the shape of the glass material 1 after the vicinity 3 of the naturally cut glass has been taken into the glass 1 on the receiving mold.

Hereinafter, the fabrication method shown in FIG. 2 will be described in more detail. The receiving die 11 is made of a cemented carbide (WC-5Ti-8C) as a base material having the size of the center portion φ20 as a transfer surface.
Using o), a thin film of a platinum-iridium-osmium alloy (Pt-Ir-Os) was coated by a sputtering method. Molten glass, zirconia (ZrO ₂₎ 8 wt Pa - St, lanthanum oxide (La ₂ O ₃₎ 30 wt Pa - St, boron oxide (B ₂ O ₃₎ 42 wt Pa - St, calcium oxide (CaO) 10 Weight A lanthanum-based glass composed of a percentage and a balance of trace components was used. After melting this glass at 1400 ° C. in a crucible of a glass melting furnace, the falling distance h is set to 100 mm, and about 2 g of molten glass 1 is dropped out from the outlet 10 maintained at 1100 ° C. Surround the glass cut area 3 with a 50 mm high heating heater 90
While heating to 0 ° C., it is supplied to the receiving mold 11 which has been heated to 430 ° C. in advance. The glass was cooled on a receiving mold to produce a glass material 1.

As a result of observing the glass material 1 obtained in this example with an optical microscope, the surface
No defects such as striae and bubbles were found. An excellent optical element could be obtained by molding this glass material.

Example 4 Glass materials having different glass compositions were manufactured by using the manufacturing method shown in FIG. Receiving mold 11
Is a platinum-tantalum-rhenium alloy (Pt-Ta-R) formed by a sputtering method using a cermet (TiC-10Mo-9Ni) as a base material with the size of the central portion φ20 as a transfer surface.
e) The thin film was coated. The molten glass is made of silicon oxide (Si
O ₂ ) 65% by weight, potassium oxide (K ₂ O) 9
Weight percent, boron oxide (B ₂ O ₃ ) 10 weight percent
Borosilicate glass consisting of 10% by weight of sodium, sodium oxide (Na ₂ O) and the balance of trace components was used. After melting this glass at 1350 ° C. in a crucible of a glass melting furnace, the falling distance h was set to 100 mm, and
Approximately 2 grams of molten glass 1 flows out of the outlet 10 maintained at 0 ° C. in the form of drops. 3 near the cut part of the glass 50 height
While being heated to 850 ° C. while being surrounded by a heating heater of mm, the material is supplied to the receiving mold 11 which has been heated to 400 ° C. in advance. The glass was cooled on a receiving mold to produce a glass material 1.

The glass material 1 obtained according to the present example was observed with an optical microscope and found to have scratches on the surface and inside.
No defects such as striae and bubbles were found. An excellent optical element could be obtained by molding this glass material.

(Embodiment 5) FIG. 3 is a process chart showing a method of manufacturing a glass material according to another embodiment of the present invention.

1 is glass (molten glass, glass material),
10 is a glass outlet, 11 is a receiving mold, 21 is a measuring means,
Reference numeral 22 denotes an atmosphere gas inlet, 23 denotes a cover, 24 denotes a temperature control means, 25 denotes a moving means, and 26 denotes a position control means. The symbol h indicates the falling distance of the glass.

FIG. 3 shows a process of manufacturing a glass material described in Embodiment 1, in which a receiving mold is placed in a non-oxidizing atmosphere, the distance between the glass outlet and the receiving mold is kept constant, and molding of an optical element is performed. The weight accuracy of the glass material for use is 1% by weight of the specified glass weight
FIG. 9 is a process diagram in which a step of performing position control is added so as to be inside.

In FIG. 3, the receiving mold is installed in a cover for maintaining a non-oxidizing atmosphere together with temperature control means and moving means. In order to prevent the receiving mold from deteriorating due to oxidation, for example, an inert gas such as nitrogen, argon, or helium, or a gas obtained by appropriately mixing hydrogen with the inert gas flows from the gas inlet, and It is kept in an oxidizing atmosphere.

When a precise optical element is formed, variations in molding conditions and performances occur due to the weight accuracy of the glass. Therefore, it is necessary to keep the variation within 1% of the predetermined glass weight. The variation factor of the glass weight of the present invention is caused by the variation of the distance between the nozzle and the receiving die. This is because the distance between the nozzle and the receiving die changes, so that the falling distance of the molten glass changes, and the natural cutting of the flowing molten glass naturally occurs. This is because the positions to be performed vary. In order to keep the distance between the glass outlet and the receiving mold constant, it is necessary to sequentially measure and adjust height variations due to the influence of heat, such as expansion and contraction of the nozzle and the receiving mold. In order to keep the distance between the nozzle and the receiving mold constant, the measuring means (for example, an optical sensor) measures the fluctuation of the height of the nozzle and the receiving mold, and the position is controlled by the position control means (for example, a servomotor). The configuration is such that the height of the mold is adjusted to the original set distance.

Hereinafter, a specific example using the manufacturing method of FIG. 3 will be described in detail.

In advance, the nitrogen is introduced through the gas inlet 22 of the cover 23.
A non-oxidizing atmosphere was created by pouring elemental gas. Receiving mold 11
Is the size of the central part diameter φ10 as the transfer surface and the base material
Using cermet (TiC-10Mo-9Ni)
Pt-Ta-Rhenium alloy (Pt-Ta)
-Re). The molten glass is silicon oxide
(SiO_Two) 30% by weight, barium oxide (BaO) 50
Wt%, boron oxide (B _TwoO_Three) 15% by weight;
A barium borosilicate glass composed of various components was used. This
Glass at 1250 ° C in a glass melting furnace crucible
After that, it flows down by the measuring means 21 and the position control means 26.
While maintaining the distance h at 50 mm, hold at 1000 ° C.
1 ± 0.01 gram of molten glass 1 from outlet 10
It flows out in the form of drops and is heated to 650 ° C by temperature control means in advance.
Is supplied to the receiving mold 11. By the temperature control means 24
While cooling the glass on the receiving mold, the moving means 25
Rotate and move the receiving mold to the glass material take-out position
Material 1 was taken out.

As a result of observing the glass material 1 obtained in this example with an optical microscope, it was found that
No defects such as striae and bubbles were found. An excellent optical element could be obtained by molding this glass material.

(Embodiment 6) FIG. 4 is a sectional view showing the shape of a glass material according to another embodiment of the present invention.

1 is glass (molten glass, glass material),
11a is a receiving mold having poor wettability, 11b is a receiving mold having good wettability, and 31 is a transfer surface of the receiving mold.

Symbols t1 and t2 in FIG. 4 indicate the thickness of the glass.

In the present invention, the receiving mold having poor wettability means a mold made of a material such as carbon, boron nitride, aluminum nitride, chromium nitride, stainless steel, nichrome, glassy carbon, and silicon carbide. The receiving mold with good wettability is coated with a thin film that has good wettability with the molten glass and is chemically stable, and the thin film is made of tungsten, tantalum, rhenium, hafnium, platinum, palladium, iridium, rhodium, It means a noble metal-based alloy thin film containing at least one or more metals among osmium and ruthenium.

As shown in FIG. 4 (a), when receiving by a receiving mold having poor wettability with the molten glass, the wettability between the glass and the receiving mold is poor and the glass thickness t due to the surface tension of the glass.
1 is thicker, so that a thick glass material having a small radius of curvature can be obtained.

As shown in FIG. 4 (b), when the glass is received by a receiving mold having good wettability with the molten glass, the glass and the receiving mold have good wettability and the glass thickness t2 is small, so that the thickness having a large radius of curvature is obtained. It can be controlled to a thin glass material.

In general, when the temperature of the receiving mold is increased, the wettability with the molten glass is improved and the wettability is improved. However, the material having poor wettability easily fuses with the molten glass and cannot be released even if cooled. The mold temperature is used at 400 ° C. or less. If the receiving mold is coated with a thin film that is wettable with the molten glass and has good wettability and is chemically stable, it is difficult to fuse with the molten glass, and the temperature of the receiving mold can be heated up to 700 ° C., so that a thin glass material is used. Is preferred. In terms of cost, since it is cheaper and easier to make a material with poor wettability, it is preferable to select a receiving material according to the use, shape, and cost of the glass material.

Further, the transfer surface 31 of the receiving mold shown in FIG. 4 (the surface with which the molten glass comes into contact) is preferably in a smooth mirror surface state. If the surface accuracy can be transferred to a glass material with a center line average roughness of 2 μm or less, Precision optical element molding can be performed stably with good performance. For this reason, the surface accuracy of the normal receiving mold is finished to a center line average roughness of 2 μm or less.

Hereinafter, a specific example using the receiving mold shown in FIG. 4 will be described.

The material of the receiving mold 11a having poor wettability shown in FIG. 4 was made of stainless steel, the radius of curvature of the transfer surface 31 was processed to 15 mm, and the surface accuracy was finished to a center line average roughness of 2 μm. Under the same conditions as in Example 1, when a glass material of 1 gram was produced, the glass thickness t1 was 6 mm. As a result of molding an optical element having a thickness of 5 mm using this glass material, an extremely high-precision optical element free from defects could be obtained.

The base material of the receiving mold 11b having good wettability shown in FIG. 4 is formed by processing a cermet (TiC-10Mo-9Ni) into a transfer surface having a radius of curvature of 15 mm and adjusting the surface accuracy to a center line average roughness of 2 μm. Finished. Then, when a 1-gram glass material was produced under the same conditions as in Example 5 using a receiving mold having good wettability coated with a thin film of a platinum-tantalum-rhenium alloy (Pt-Ta-Re) by sputtering. The glass thickness t2 could be controlled to 4 mm, which was thinner than t1. As a result of molding an optical element having a thickness of 3 mm using this glass material, an extremely high-precision optical element having no defects was obtained.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the composition of the optical glass, the shape of the glass material, the method of heating the glass melting furnace or the receiving mold described in each embodiment.
It is not limited to conditions and the like.

[0073]

According to the present invention, it is possible to obtain a glass material for a reheat press having a desired shape without defects on the surface and inside of the glass by a simple method that does not require grinding and polishing steps. This has a remarkable effect on improving the performance and reducing the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for producing a glass material according to one embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing a glass material according to another embodiment of the present invention.

FIG. 3 is a process chart showing a method for manufacturing a glass material according to another embodiment of the present invention.

FIG. 4 is a sectional view showing a shape of a glass material according to another embodiment of the present invention.

FIG. 5 is a process chart showing a conventional method for manufacturing a glass material.

FIG. 6 is a process chart showing a method of manufacturing another conventional glass material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass (molten glass, glass material) 2 Cutting part 3 Near cutting part 4 Surface tension of glass 5 Defect of glass 10 Glass outlet 11 Receiving mold 12 Heating means 13 Cutting blade 21 Measuring means 22 Gas inlet 23 Cover 24 Temperature control Means 25 Moving means 26 Position control means 31 Transfer surface of receiving mold 11a Receiving mold having poor wettability 11b Receiving mold having good wettability

──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Inoue 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Toshihiko Muroi 1-28 Kandasudacho, Chiyoda-ku, Tokyo Sumita (56) References JP-A-2-14839 (JP, A) JP-A-63-297224 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 7/00 -7/22 C03B 9/00-17/06

Claims (15)

(57) [Claims] 1. A method of manufacturing a glass material for molding an optical element, wherein a molten glass flowing down from a glass outlet of a glass melting furnace is received and cooled by a receiving die, and a distance between the receiving die and the glass outlet is set to a receiving die. A method for producing a glass material for molding optical elements, characterized in that the molten glass that has flowed down into the glass is naturally cut by its own weight and surface tension, and the temperature of the molten glass flowing down in the vicinity of the cut portion is within the range of the softening temperature or higher. 2. The method for producing a glass material for molding optical elements according to claim 1, wherein the vicinity of the cut portion of the molten glass flowing down from the glass outlet is heated to a temperature not lower than the softening temperature of the glass. 3. The method for producing a glass material for molding an optical element according to claim 1, wherein the receiving mold is subjected to temperature control to receive the molten glass. 4. The glass temperature equal to or higher than the softening temperature is equal to or lower than 4.5 × 10 ⁷ poise in viscosity of the glass.
3. The method for producing a glass material for molding an optical element according to item 1. 5. The temperature of the molten glass in the glass melting furnace is 5
The method for producing a glass material for molding an optical element according to claim 1, wherein the temperature is from 00 to 1300 ° C. 6. The method for producing a glass material for molding an optical element according to claim 1, wherein the crucible of the glass melting furnace and the outlet of the glass are made of platinum. 7. The method for producing a glass material for molding an optical element according to claim 1, wherein the receiving mold is present in a non-oxidizing atmosphere. 8. The position of the receiving die is controlled so that the distance between the glass outlet and the receiving die is kept constant, and the weight accuracy of the glass material for forming an optical element is within 1% of a predetermined glass weight. 2. The method for producing a glass material for molding an optical element according to item 1. 9. Due to the wettability of the receiving mold with the molten glass,
The method for producing an optical element molding glass material according to claim 1, wherein the thickness of the optical element molding glass material is controlled. 10. The receiving mold according to claim 9, wherein the receiving mold is at least one selected from carbon, boron nitride, aluminum nitride, chromium nitride, stainless steel, nichrome, glassy carbon, and silicon carbide having poor wettability with the molten glass. The method for producing a glass material for molding an optical element according to the above. 11. The method according to claim 9, wherein the receiving mold is coated with a chemically stable thin film having good wettability with the molten glass. 12. The thin film is made of tungsten, tantalum, rhenium, hafnium, platinum, palladium, iridium,
The method for producing a glass material for molding an optical element according to claim 11, wherein the thin film is a noble metal-based alloy thin film containing at least one metal selected from rhodium, osmium, and ruthenium. 13. The method for producing an optical element molding glass material according to claim 3, wherein the temperature of the receiving mold is a temperature at which the molten glass and the receiving mold can be released after cooling the molten glass without fusing. 14. The method according to claim 13, wherein the temperature of the receiving mold is 700 ° C. or less. 15. The method for producing a glass material for molding an optical element according to claim 1, wherein the surface roughness of the receiving die is a mirror surface having a center line average roughness (Ra) of 2 μm or less.